Perpendicular magnetic recording has been developed in part to achieve higher recording density than is realized with longitudinal recording devices. A PMR write head typically has a main pole layer with a small surface area at an air bearing surface (ABS), and coils that conduct a current and generate a magnetic flux in the main pole such that the magnetic flux exits through a write pole tip and enters a magnetic medium (disk) adjacent to the ABS. Magnetic flux is used to write a selected number of bits in the magnetic medium and typically returns to the main pole through two pathways including a trailing loop and a leading loop where both involve a shield structure. The trailing loop comprises a trailing shield structure with first and second trailing shields each having a front side at the ABS. The leading loop includes a leading shield with a front side at the ABS and connected to a return path proximate to the ABS. The return path extends to the back gap connection and enables magnetic flux in the leading loop pathway to return from the leading shield through the back gap connection to the main pole layer.
For both conventional (CMR) and shingle (SMR) magnetic recording, continuous improvement in storage area density is required for a PMR writer. A write head that can deliver or pack higher bits per inch (BPI) and higher tracks per inch (TPI) is essential to the area density improvement. A fully wrapped around shield design for a PMR write head is desired where the trailing shield is responsible for improving down track field gradient while side shields and a leading shield enhance the cross track field gradient and TPI as well as improve adjacent track erasure (ATE) also known as ATI.
The key to an optimized PMR writer structure is the capability to control distribution of magnetic flux from the main pole to each shield. Ideally, better control of magnetic flux in the near field or proximate to the main pole is desirable to achieve an enhanced near field gradient and to realize higher area density capability (ADC). Typically, flux distribution is controlled by changing the magnetic saturation (Ms) of materials in the shields, and by modifying geometries (size and shape) of the shields. In today's PMR design, most shield optimization efforts have focused on the side shields and trailing shield, and substantially less emphasis on the leading shield. However, in order to achieve higher performance capability associated with PMR writers that require higher TPI capability to at least 400K/in2 for CMR and at least 500K/in2 for SMR, a better design is needed for the leading shield structure.